2Bot

2Bot is a FastMCP server that lets ChatGPT (or any MCP client) call your local Codex CLI through a controlled MCP tool.

• MCP server name is fixed to 2Bot.
• Local mode uses stdio.
• Remote mode uses HTTP (Streamable HTTP) for ChatGPT-compatible deployments.

What 2Bot does

2Bot exposes a single typed tool, run_codex_prompt, which runs codex exec --json - safely:

• no shell=True
• prompt passed via stdin
• timeout handling
• working-directory validation and allowlist support
• JSON-serializable structured output

Installation

python -m venv .venv
source .venv/bin/activate
pip install -e .

For tests:

pip install -e .[dev]
pytest

Configuration

2Bot is environment-driven.

Variable	Default	Description
TWOBOT_TRANSPORT	stdio	stdio or http
TWOBOT_HOST	127.0.0.1	HTTP bind host
TWOBOT_PORT	9000	HTTP bind port
TWOBOT_BASE_URL	unset	Optional public HTTPS URL for docs/ops
TWOBOT_LOG_LEVEL	INFO	Logging level
TWOBOT_ENABLE_NO_AUTH	true	Enable no-auth mode for initial ChatGPT testing
CODEX_ALLOWED_ROOTS	unset	Optional cwd allowlist (:-separated on macOS/Linux)

Authentication note: for first connection tests, use no auth. For production, prefer standards-based MCP-compatible auth in front of or integrated with this service.

Local mode (stdio)

Run with stdio (default):

2bot-mcp
# or
python -m twobot_codex_mcp.server

You can also force stdio:

TWOBOT_TRANSPORT=stdio 2bot-mcp

Remote mode (HTTP / Streamable HTTP)

Run HTTP mode locally on loopback:

TWOBOT_TRANSPORT=http TWOBOT_HOST=127.0.0.1 TWOBOT_PORT=9000 2bot-mcp

Or with explicit CLI flags:

2bot-mcp --transport http --host 127.0.0.1 --port 9000

Expose via HTTPS for ChatGPT

ChatGPT must reach a public HTTPS URL. Typical setup:

1. Run 2Bot in HTTP mode on 127.0.0.1:9000.
2. Put a reverse proxy or tunnel in front (Nginx, Caddy, Cloudflare Tunnel, etc.).
3. Publish a TLS endpoint like https://mcp.example.com forwarding to http://127.0.0.1:9000.
4. Configure ChatGPT custom MCP connection to that public URL.

ChatGPT connection notes

ChatGPT connects to the remote HTTPS MCP endpoint, not to stdio.

High-level flow:

1. Start 2Bot in HTTP mode.
2. Expose the endpoint at a public HTTPS URL.
3. Create/connect the custom MCP app in ChatGPT pointing at that URL.

Use URL pattern:

• https://<your-public-hostname>/ (or the exact path your reverse proxy maps to the FastMCP HTTP app)

Security notes (important)

Exposing a tool that can execute local Codex workflows is sensitive.

Recommendations:

• Restrict CODEX_ALLOWED_ROOTS to minimal directories.
• Keep conservative defaults (sandbox=read-only, allow_edits=false).
• Avoid danger-full-access unless absolutely necessary and trusted.
• Prefer private deployments (VPN, private network, authenticated gateway).
• Do not expose an unrestricted instance on the public internet casually.

Example deployment notes

1) Local-only HTTP bind

TWOBOT_TRANSPORT=http TWOBOT_HOST=127.0.0.1 TWOBOT_PORT=9000 2bot-mcp

2) Reverse proxy / tunnel

• Proxy https://mcp.example.com -> http://127.0.0.1:9000
• Keep TLS at the edge
• Keep 2Bot private behind the proxy where possible

3) Keep stdio mode for local MCP clients

TWOBOT_TRANSPORT=stdio 2bot-mcp

Tool reference: run_codex_prompt

Parameters:

• prompt: str
• cwd: str | None = None
• model: str | None = None
• profile: str | None = None
• sandbox: "read-only" | "workspace-write" | "danger-full-access" = "read-only"
• approval_policy: "untrusted" | "on-request" | "never" | None = None
• allow_edits: bool = False
• skip_git_repo_check: bool = False
• add_dirs: list[str] | None = None
• timeout_sec: int = 1800
• ephemeral: bool = True
• include_event_log: bool = False

Behavior is preserved from local mode while adding transport/config flexibility.